Pneumatic hand tool exhaust muffler

ABSTRACT

A muffler (30) for quieting exhaust expelled from a pneumatic hand tool (10) having a handle (12), an air intake port, and an exhaust port. The muffler (30) includes an inner tube with a plurality of holes, a number of washers (36) positioned longitudinally about the inner tube (32) at the location of the plurality of holes, and an end cap for sealing off the inner tube. The inner tube is preferably formed as a spring. During use, exhaust air pass from the hand tool (10) into the inner tube, into the washers, through the washers, and out the muffler end cap. Alternative embodiments includes an outer tube.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.08/999,588 filed Jan. 13, 1998.

FIELD OF THE INVENTION

The present invention relates to acoustics and sound modifying means formuffling and filtering air, and more particularly to devices formuffling and filtering air exhausted from pneumatically-operated handtools, equipment, machines, and the like.

BACKGROUND OF THE INVENTION

Pneumatic hand tools are commonly used in industrial and residentialsettings. Various types of pneumatic hand tools are available, includingratchets, drills, wrenches, grinders, sanders, etc. Known hand toolstypically include a handle having a hollow internal chamber. The chamberincludes an air intake passage and an air exhaust passage. Each passageextends between a motor and an opening in the bottom surface of thehandle. The portion of the intake passage located near its respectivehandle opening includes components adapted to connect to a standard aircoupler or the like. The coupler is in communication with a pressuredair supply source. The exhaust passage opens to the atmosphere. Whenexhaust air is vented from the hand tool, a considerable amount of noiseand particulate debris is generated, potentially causing auditory and/orrespiratory damage to the operator and others located nearby.

Although ear plugs and face masks are available to workers, they areoften not used for a number of reasons--most typically because they arenot convenient. Numerous attempts have been made by hand toolmanufacturers, therefore, to reduce the amount of noise and particlesgenerated by the hand tool itself. These attempts include designingquieter and cleaner motors and designing hand tool components thatsuppress noise and trap waste prior to expulsion from the hand tool. Forexample, U.S. Pat. No. 5,418,339 describes a pneumatic hand tool havingan exhaust port filled with a web of non-woven fibers coated with abinder resin. These types of mufflers have had some success in mufflingsound, but there is often an increase in back pressure to the motorcausing a decrease in the operating efficiency of the hand tool. Theoperating efficiency of a tool is typically measured in the operatingspeed of the motor in revolutions per minute (rpm) at a certain gaugepressure.

Cylindrical canister-type combination muffler and air filters are knownfor large machines, such as hoists and presses. For example, U.S. Pat.No. 4,134,472 describes a combination muffler and air filter having acentral tubular member with a number of slots. The tubular member issurrounded by a disposable canister having inner and outer perforatedrigid cylinders encasing a series of stacked annular filter members.Exhaust air passes through the inner cylinder, into the filters, and outthe outer cylinder. These devices are not typically used for hand tools,however, because of they are large, heavy, and difficult to maneuver.

Thus, there exists a need for a noise muffling system that can reducesound levels and remove entrained solid and liquid contaminates from theexhausted air before it is discharged to the atmosphere. The idealdevice would effectively muffle and filter the exhaust air withoutcreating substantial amounts of back pressure. This would allow a handtool to be operated without jeopardizing performance of the pneumatictool over long periods of usage. The ideal muffling system would furtherattach to a hand tool body and remain attached even during significanttool vibrations. In addition, it would be desirable to have a mufflerthat can be easily attached to existing pneumatic hand tools. Thepresent invention is directed to fulfilling this need.

SUMMARY OF THE INVENTION

In accordance with aspects of the present invention, a mufflerimprovement for quieting exhaust expelled from a pneumatic hand tool isprovided. The hand tool has a handle with an exhaust passage. Themuffler includes an inner tube having distal and proximal ends andvarious airflow openings. The muffler further includes a number ofwashers positioned longitudinally about the inner tube. The combinationof the inner tube and washers are located within the handle exhaustpassage. An end cap is provided for closing off the inner tube distalend. During hand tool use, exhaust air enters the inner tube, flows outthe inner tube airflow openings into the number of washers, and out theend cap. In preferred embodiments, the inner tube is a spring.

In accordance with aspects of this invention, the washers are placedside-by-side along the inner tube and are of equal densities. Inalternative embodiments, the washers are placed side-by-side and are ofdiffering densities. In further alternative embodiments, washers eachdirectly contact the inner tube. The washers are preferably formed froma material in the group comprising felt, gauze, rubber, foam, andsynthetic fiber. In one embodiment, the washers include washers ofdiffering inner diameters so that a portion of the washers does notcontact the inner tube.

In accordance with aspects of this invention, another embodiment of amuffler for quieting exhaust expelled from a pneumatic hand tool isprovided. The muffler includes an inner tube having airflow passages.The inner tube also includes a proximal end adapted to connect to thepneumatic hand tool. The muffler further includes a number of absorptivewashers positioned longitudinally about the inner tube at the locationof the airflow passages and an outer sleeve positioned about thecombination of washers and inner tube. The outer sleeve is formed from amaterial having a plurality of passage through which air may pass.During use, exhaust air passes from the hand tool out the exhaust port,into the inner tube, out the inner tube airflow passages, through thewashers, and out the outer sleeve passages. In preferred embodiments,the inner tube is a spring. In one embodiment, the muffler furtherincludes first and second end seals. The washers include first and lastwashers, the first end seal being located adjacent the first washer, thesecond end seal being located adjacent the last washer.

In accordance with aspects of this invention, yet another embodiment amuffler for quieting exhaust expelled from a pneumatic hand tool isprovided. The muffler includes a spring inner tube having proximal anddistal ends. The inner tube further includes first and second sectionsand a plurality of airflow passages. The first section is adapted to belocated within the handle exhaust passage. The second section is adaptedto be located outside the handle. A number of washers are positionedabout the inner tube at least at the location of the spring inner tubeairflow passages. An outer sleeve is positioned about at least a portionof the combination of washers and spring inner tube. The outer sleevehas a plurality of passages through which air may be expelled.Attachment means are provided to connect the muffler with the handle.During use, exhaust air passes into the spring inner tube, out thespring inner tube airflow passages, through the washers, and out theouter sleeve. In one embodiment, the outer sleeve is formed from amaterial in the group comprising woven nylon, canvas, synthetic fabric,tape, sealant, plastic, rubber, and synthetic fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial cross-sectional side view of a first embodimentmuffler formed in accordance with the present invention;

FIG. 2A is a partial cross-sectional side view of a second embodiment ofa muffler formed in accordance with the present invention;

FIG. 2B is a plan view of a lower cap shown in FIG. 2A;

FIG. 3A is a cross-sectional side view of a third embodiment of amuffler formed in accordance with the present invention;

FIGS. 3B and 3C are plan views of upper and lower fittings shown in FIG.3A;

FIG. 4A is a cross-sectional side view of a fourth embodiment of amuffler formed in accordance with the present invention;

FIG. 4B is a view of an end cap taken along lines 4B--4B of FIG. 4A;

FIG. 5A is a cross-sectional side view of a fifth embodiment mufflerformed in accordance with the present invention;

FIG. 5B is a plan view of the distancing washer shown in FIG. 5A;

FIG. 6A is partial cross-sectional side view of a sixth embodiment of amuffler formed in accordance with the present invention; and

FIG. 6B is a plan view of a lower cap taken along lines 6B--6B of FIG.6A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is a muffler for use in quieting exhaust expelledfrom a pneumatic hand tool. The present invention is compact,lightweight, and easy to use. In select embodiments, the muffler isadapted for immediate connection to known pneumatic hand tools, withonly minimal changes required to the hand tool. A number of embodimentsof the present invention are described below with reference to theaccompanying drawings. It should be appreciated that these embodimentsare provided to illustrate various features of the present invention,and thus should not be viewed as limiting with regard to the specificcombination of their configurations.

Referring to FIG. 1, a pneumatic hand tool 10 generally includes ahandle 12 within which an air intake passage 14 and an air exhaustpassage 16 extend and end at respective openings in the bottom surface18 of the handle. The air intake passage opening includes threads 20adapted to connect to an air supply line 15 via a standard air coupler22 or the like. The supply line 15 is in communication with a pressuredair supply source (not shown.) A muffler formed in accordance with thepresent invention connects to the exhaust passage 16 using any one of anumber of means, depending on the handle configuration of the tool.

Shown in FIG. 1 is a first embodiment of a muffler 30 formed inaccordance with the present invention. FIG. 1 is a partial cutawaydrawing. At the location of the muffler 30, the inner tube 32 is shownin side view, not in cross-sectional side view. The muffler 30 includesan inner tube 32 having proximal and distal ends 38, 40, an outer sleeveor tube 34, and a number of washers 36. Each washer is preferablycircular with a centered circular inner hole. The inner tube 32 ispositioned within the area defined by the stacked washer inner holes.The inner tube 32 is formed from a relatively lightweight rigidmaterial, e.g., plastic, metal alloys, steel, etc. The inner tube 32includes a plurality of holes 42 distributed about the inner tube alongits longitudinal length. In the embodiment of FIG. 1, the inner tubeproximal end 38 preferably includes outer threads 44 adapted to screwinto corresponding threads formed in the exhaust passage 16 near theexhaust opening. Other known attachment means, however, may be used,e.g., adhesive, latches, clamps, snaps, bolts, crosspins, etc.

Still referring to FIG. 1, the washers 36 are similarly sized to oneanother and are positioned side-by-side so that their inner holes arealigned. The inner tube 32 is located within the area defined by thealigned washer holes. The number of washers 36 should be sufficient toextend the length of the inner tube for which there are holes. Thewashers 36 are made of a suitable sound dampening and/or filteringmaterial such as felt, gauze, rubber, foam, fiber, synthetics, etc. Thewashers should be of a density sufficient to dampen the noise, but notdense enough to cause a significant back pressure in the exhaust passage16. An exemplary high density felt washer that has yielded good resultsis manufactured by All Felt Products of Engleside, Ill., product numberF-1 S.A.E. During testing, this washer decreased the noise level byapproximately 15 decibels, while causing a back pressure of less thanabout 2.5 psi as measured in a standard pneumatic hand tool. Inaddition, the washers preferably include mold and moisture-resistingchemicals.

As shown in FIGS. 1, 3, and 4, the washer inner hole diameters are allthe same size, and the washer outer diameters are all the same size. Ingeneral, a muffler formed in accordance with the present invention mayinclude washers of various inner and outer diameters. For example, theconfigurations of FIGS. 2A and 5A show washers of like outer diametersand varying inner diameters. In addition, the washers may be of varyingdensities and/or thickness'. The size, density, and arrangement of thewashers will affect the rate at which the exhaust air is slowed andhence will effect exhaust noise and back pressure. Accordingly, adesigner should carefully consider the number, size, density, material,and placement of the washers 36 in the muffler.

The combination of washers 36 and inner tube 32 is located within theouter sleeve 34. Referring back to the embodiment of FIG. 1, the outersleeve 34 is sized to contact the outer perimental surfaces of thewashers. The outer sleeve 34 is preferably formed from a lightweightflexible fabric that includes air passages. Example flexible materialsinclude loose-knit or woven nylon fabric, canvas, polyester, wool,perforated flexible plastic, perforated tape, other synthetic fabrics,perforate sealant, etc. It is also possible to form the outer sleeveform a rigid material, e.g., rigid plastic, perforated metal or metalfoil, etc.

Still referring to FIG. 1, the washers extend along the inner tubebetween the tube distal end and the inner tube location adjacent theproximal end threads. A lower seal or cap 50 closes off the inner tubedistal end 40 and the last washer which is positioned at the distal end.An upper sealant or cap 50' closes off the end washer near the proximalend. Although the caps 50, 50' may be flexible or rigid, they do notallow airflow therethrough in the embodiment of FIG. 1. During use,exhaust air enters the inner tube proximal end 38 from the exhaustpassage 16, travels down the inner tube and outward through the innertube holes and into the washers. At the washers 36, the exhaust isslowed and the exhaust noise is consequently reduced. The exhaust airthen travels radially out the washers and through the outer sleeve 34air passages to the atmosphere. As will be appreciated from viewing FIG.1, the caps on the first and last washers force the exhaust air totravel radially outward through the washers.

Shown in FIGS. 2A and 2B is a second embodiment of a muffler 30 formedin accordance with the present invention. FIG. 2A is also a partialcutaway drawing. At the location of the handle 12 and the muffler 30,the inner tube 32 and the components labeled 56 and 72 are shown in sideview, not in cross-sectional side view. Similar to the first embodiment,the second embodiment also includes an inner tube 32 having proximal anddistal ends 38, 40, and a plurality of holes 42 therethrough. Themuffler 30 further includes a first portion 39 and a second portion 41.The first portion 39 is located near the inner tube proximal end 38. Thesecond portion 41 is located near the distal end 40. The holes 42 arelocated at least along the length of the inner tube second portion 41.The first portion is surrounded by a plurality of similarly-sizedstacked circular washers 36. The combination of the first portion andits respective washers is positionable within the exhaust passage 16 viathe exhaust opening. The outer diameters of these washers are preferablysized to contact the surface of the exhaust passage inside the handle.

The second portion 41 is surrounded by washers and an outer sleeve 34.The outer sleeve includes first and second ends 68, 70. The outer sleevefirst end 68 is located between the proximal and distal inner tube ends38, 40. The outer sleeve second end 70 is located near the inner tubedistal end 40. The outer sleeve first end 68 is formed as a rigidannular member 72 that includes a threaded outer surface 73. As shown inFIG. 2A, the handle exhaust opening is modified to include matingthreads 74 adapted to engage the outer sleeve first end threaded outersurface 73. The mating threads 74 may be formed from a nut that isinserted in the exhaust opening, formed integrally at the exhaustopening during manufacture of the handle, formed at the opening afterformation of the handle, or formed using any other methods available forcreating threading. The mating threads of FIG. 2A are provided by acylindrical nut that is glued, cemented, or heat welded to an existinghandle exhaust opening. What is important to the second embodiment ofthe present invention is that the nut be securely attached to the handleso that it will not move during use of the hand tool.

Still referring to FIG. 2A, washers 36 of differing densities arearranged alternatingly along the inner tube 32. In addition to densityvariations, some of the washers along the inner tube second portion havea larger inner diameter than other of the washers. This provides apassage 54 for exhaust air to travel in addition to passage out thewashers. The second embodiment muffler includes a perforated lower endcap 56 shown in plan view in FIG. 2B. The perforated lower cap includesa ring of holes 58 positioned to align with the passage 54 during use.

A third embodiment of a muffler 30 formed in accordance with the presentinvention is shown in FIGS. 3A-3C. FIG. 3A is a partial cutaway drawing.At the location of the muffler 30, the inner tube 32 and the componentslabeled 64 and 64 are shown in side view, not in cross-sectional sideview. Referring particularly to FIG. 3A, this embodiment is similar tothe first embodiment except that the inner tube is of a significantlylonger length so that the inner tube holes and washers arecorrespondingly located farther from the hand tool 10. In addition,longitudinal spaces 60 are left between the washers. This arrangementprovides noise reduction with even less amounts of back pressure than ineither the first or second embodiments.

Upper and lower support fittings 62, 64 are used to cap the first andlast washers. As shown in FIG. 3B, the upper support fitting 62completely prohibits airflow. As shown in FIG. 3C, the lower supportfitting 64 includes a number of openings 65 that allow airflowtherethrough. Both the upper and lower support fittings 62, 64 include acentral hole 67 through which the inner tube 32 extends. Both fittings62, 64 additionally include an arm 66 adapted to attach to an air supplyline 15. The attachment to the supply line helps to steady and supportthe muffler during use.

Fourth and fifth embodiments of a muffler 30 formed in accordance withthe present invention are shown in FIGS. 4 and 5. These embodimentsfurther stabilize the muffler 30 by forming the muffler about the supplyline 15. In the fourth embodiment of FIGS. 4A and 4B, the handle exhaustopening is separate from the intake opening, similar to the handleconfiguration shown in FIG. 1. In the fifth embodiment of FIGS. 5A and5B, the handle is formed to cause the exhaust passage 16 to surround theair intake passage 14. In general, both the fourth and fifth mufflerembodiments include a perforate outer sleeve 34 surrounding a pluralityof washers 36. There is no inner tube, instead the washers 36 aredisposed about the air supply line 15. The muffler is closed at itsdistal end using a sealant or capping means 79 that may includeperforations, depending on the flow requirements of a particularapplication.

Referring to FIGS. 4A and 4B, a Y-shaped attachment piece 90 is providedto connect the supply line 15 and muffler 30 with the air intake passage14 and the exhaust passage 16, respectively. The Y-shaped attachmentpiece has an input arm 92 and an output arm 94 that connect directly toa standard coupler 22 and the exhaust passage 16 at the handle,respectively. The output arm 94 connects with the input arm 92 andsurrounds it to form a single combined arm 96. The outer sleeve andwasher components attach to the combined arm 96, with the supply line 15passing through the washers inner holes.

Referring to the embodiment of FIGS. 5A and 5B, the supply line 15 isconnected to the intake passage 14 via a standard coupler 22. A portion80 of the handle exhaust passage is formed to envelope the intakeopening and portions of the coupler 22. The muffler proximal end isadapted to connect to this exhaust passage portion 80. The mufflerproximal end includes a coupler mating piece 82 and a rigid distancingwasher 84. The mating piece 82 is held in the outer sleeve 34 by thedistancing washer 84. The coupler mating piece 82 receives the standardcoupler 22 at one end and connects to the air supply line 15 at theother end. The coupler mating piece 82 is of a smaller outer diameter soexhaust air is forced to pass around it and the supply line 15 and intothe muffler washers 36.

Shown in FIGS. 6A and 6B is a sixth embodiment of a muffler formed inaccordance with the present invention. The muffler includes an innertube 32 and a number of washers 36. The inner tube 32 is preferablyformed as a spring. FIG. 6A is a partial cutaway drawing. At thelocation of the muffler, the inner tube 32 is shown in side view, not incross-sectional side view. The inner tube 32 is positioned within thearea defined by the stacked washer inner holes. When using a springinner tube, the coil thickness and the number of coils per a givenlength can be tailored to give a particular desired air flow rate. Thespring inner tube may be in compression, in tension, or otherwiseunloaded. What is important to the present invention is the airflow rateensuing from the spring, not necessarily the capability of the spring.Therefore, other spring-like shapes may be used.

In the embodiment of FIG. 6A, the combination of washers and inner tubeare inserted directly into the air exhaust passage 16. The interiorsurfaces of the handle exhaust passage act as an outer tube. The washersare sized to provide airflow space between the peripheral edge surfacesof the washers and the air exhaust passage side wall surfaces. An endcap 100 is provided to close off the exhaust passage at the handlebottom surface 18. The cap 100, shown in FIG. 6B, includes one or moreopenings 102 through which exhaust gas may exit the hand tool. It ispreferable, that the cap 100 does not include openings that aligndirectly with the inner tube so that exhaust gas will pass from theinner tube laterally outward through the washers before exiting thetool. During use, exhaust passes from the tool through the inner tube32, out the washers, and through the passages to the openings in the endcap.

As will be appreciated from a reading of the above, the presentinvention is a compact, lightweight, and easy to use device capable ofeffectively quieting exhaust expelled from a pneumatic hand tool whilecausing minimal amounts of back pressure on the pneumatic motor. Thepresent invention may be attached to known hand tools with only minorchanges required to the hand tool.

While the preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. In a pneumatic hand toolhaving a handle with an exhaust passage, a muffler improvementcomprising:(a) an inner tube having airflow openings, the inner tubehaving distal and proximal ends; (b) a number of absorptive washerspositioned longitudinally about the inner tube; the combination of theinner tube and washers being located within the handle exhaust passage;and (c) an end cap for closing off the inner tube distal end; whereinduring hand tool use, exhaust air enters the inner tube proximal end,flows out the inner tube airflow openings into the number of washers,and out the end cap.
 2. The muffler according to claim 1, wherein theinner tube is a spring.
 3. The muffler according to claim 1, wherein thenumber of washers are placed side-by-side along the inner tube and areof equal densities.
 4. The muffler according to claim 1, wherein thenumber of washers are placed side-by-side and are of differingdensities.
 5. The muffler according to claim 1, wherein the number ofwashers each directly contact the inner tube.
 6. The muffler accordingto claim 1, wherein the number of washers are formed from a material inthe group comprising felt, gauze, rubber, foam, and synthetic fiber. 7.The muffler according to claim 1, wherein the number of washers includewashers of differing inner diameters so that a portion of the washersdoes not contact the inner tube.
 8. A muffler for quieting exhaustexpelled from a pneumatic hand tool, the hand tool having a handle withan exhaust port, the muffler comprising:(a) an inner tube having airflowpassages, the inner tube including a proximal end adapted to connect tothe pneumatic hand tool exhaust port; (b) a number of absorptive washerspositioned longitudinally about the inner tube at the location of theairflow passages; and (c) an outer sleeve positioned about thecombination of washers and inner tube, the outer sleeve being formedfrom a material having a plurality of passages through which air maypass;wherein during use, exhaust air passes from the hand tool out theexhaust port, into the inner tube, out the inner tube airflow passages,through the washers, and out the outer sleeve passages, wherein theinner tube is a spring.
 9. A muffler for quieting exhaust expelled froma pneumatic hand tool, the hand tool having a handle with an exhaustport, the muffler comprising:(a) an inner tube having airflow passages,the inner tube including a proximal end adapted to connect to thepneumatic hand tool exhaust port; (b) a number of absorptive washerspositioned longitudinally about the inner tube at the location of theairflow passages; and (c) an outer sleeve positioned about thecombination of washers and inner tube, the outer sleeve being formedfrom a material having a plurality of passages through which air maypass;wherein during use, exhaust air passes from the hand tool out theexhaust port, into the inner tube, out the inner tube airflow passages,through the washers, and out the outer sleeve passages, wherein thenumber of washers are placed side-by-side and are of differingdensities.
 10. A muffler for quieting exhaust expelled from a pneumatichand tool, the hand tool having a handle with an exhaust passage, themuffler comprising:(a) a spring inner tube having proximal and distalends, the inner tube further including first and second sections and aplurality of airflow passages, the first section being adapted to belocated within the handle exhaust passage, the second section beingadapted to be located outside the handle; (b) a number of washerspositioned about the inner tube at least at the location of the springinner tube airflow passages; (c) an outer sleeve positioned about atleast a portion of the combination of washers and spring inner tube, theouter sleeve having a plurality of passages through which air may beexpelled; and (d) attachment means adapted to connect the muffler withthe handle; wherein during use, exhaust air passes into the spring innertube, out the spring inner tube airflow passages, through the washers,and out the outer sleeve.
 11. The muffler according to claim 10, whereinthe number of washers are placed side-by-side along the inner tube andare of equal densities.
 12. The muffler according to claim 10, whereinthe number of washers are formed from a material in the group comprisingfelt, gauze, rubber, foam, and synthetic fiber.
 13. The muffleraccording to claim 10, further comprising an end cap for sealing thedistal end of the muffler.
 14. The muffler according to claim 10,wherein the outer sleeve is formed from a material in the groupcomprising woven nylon, canvas, synthetic fabric, tape, sealant,plastic, rubber, and synthetic fiber.